The subject of the present invention is a method for processing metallized packaging materials, especially beverage cartons like Tetra Pak, ELOPAK, etc., or transparent (blister) packaging.
Despite their name, beverage cartons are not made of cardboard alone, but contain several closely compounded layers of cardboard and plastic—as well as aluminum for longer life products such as juice and milk. Aluminum protects the product against oxygen and light. In 2006, beverage cartons contained only 60-76 percent pulp, 13-34 percent plastic, and 0-6 percent aluminum. The plastic layer is usually polyethylene.
Tetra Pak is a brand of beverage cartons sold since the 1950s by the Swedish company of the same name and common throughout the world, particularly as packaging for milk. The brand name has become an everyday German term synonymous with beverage cartons.
At the moment, it is mainly the pulp content, i.e. the fibers, that is recycled from the beverage cartons collected for recycling. The fibers are re-used in the production of paper, cardboard, and paperboard. The plastic content, which has increased substantially in the meantime, is usually used to generate energy, i.e. it is incinerated, and the aluminum content is also incinerated as a substitute for bauxite in the cement industry. In many cases, the plastic and aluminum fractions are only pressed into bales and then go to landfill. This residue is thus only used as a substitute for primary fuel or goes to landfill.
With the aid of special molding processes, the shredded beverage cartons are used to make simple objects (fruit crates, etc.) without specific quality requirements. For this purpose, the plastics present are melted as composite material, while the residual fibers, aluminum, and residual materials are included in the molding process.
There are also recycling concepts where the plastic fraction is oiled and the aluminum is recovered in the form of flakes.
In a different process, the rejects, i.e. the plastic films and aluminum foils, undergo pyrolysis in a gas reactor at temperatures of over 400° C. In this process, the polyethylene begins to gasify (pyrolysis gas) upwards of 400° C., while the aluminum remains in solid form at this temperature. However, the aluminum produced is an agglomerate that is contaminated with non-gasified impurities (mainly carbon compounds, but also other metals). The combustible pyrolysis gas then provides electrical and thermal energy when it is incinerated. A method in which the plastic fraction is gasified in a fluidized bed is described, for example in WO 00/09771 A1 or in WO 00/09770 A1.
WO 97/49494 A1 describes a method where the metallized packaging material is shredded with the aid of a refiner and the fibers are recovered by means of a drum pulper.
In another recycling process, the rejects are treated with a plasma jet at a temperature of more then 1100° C. The aluminum in the rejects does leave the process in re-usable form as bars, but this process is very energy-intensive.
Recovery of the individual components in beverage cartons as real valuable materials, i.e. without incineration of the plastic fraction, has been contemplated in various ways and tested in pilot plants, but has never been applied yet anywhere on an industrial scale.
For example, WO 2010/052016 A2 describes a method where the shredded plastic waste is separated using heavy media separation. Here, selective solvent treatment is also applied, which causes the individual plastic components to dissolve, thus separating them from the metal or other plastic components. With this method, different plastic layers can be recovered individually. Both the fibrous material and the aluminium layer result as separate fractions.
DE 31 10 254 A1 describes a recycling process for blister packaging, whose uses include packaging of pharmaceuticals in tablet or capsule form. In this case, the aluminum-PVC reject foils/films are granulated, mixed with additives, and used as basic material for thermoplastics. Separate recovery of plastic and aluminum is not possible with this method.